Facebook has banned Cambridge Analytica, a data analytics firm that played a key role in multiple populist political campaigns, including Brexit and the presidential campaign of Donald Trump.

Facebook announced that it would ban the account of Cambridge Analytica’s parent company, Strategic Communication Laboratories, in addition to the accounts of Aleksandr Kogan, a psychologist at the University of Cambridge, and Christopher Wylie, an employee of Eunoia Technologies.

In their post explaining the ban, Facebook said that Kogan passed user data obtained via Facebook to Cambridge Analytica and to Wylie, and that both Wylie and Cambridge Analytica failed to delete this data.

Facebook conceded that Kogan “gained access to this information in a legitimate way and through the proper channels that governed all developers on Facebook at that time,” but said by passing the data to third parties “he did not subsequently abide by our rules.”

In 2015, when Facebook learned that Kogan had shared the results of his research on Facebook users with Cambridge Analytica and Wylie, they asked them to delete the data, and received assurances from both that this had been done.

Facebook said that their decision to ban Cambridge Analytica’s parent company was made on the basis of reports that they are currently investigating.

Several days ago, we received reports that, contrary to the certifications we were given, not all data was deleted. We are moving aggressively to determine the accuracy of these claims. If true, this is another unacceptable violation of trust and the commitments they made.

Cambridge Analytica has been at the heart of several high-profile campaigns on the political right. The company initially attracted Ted Cruz as a client during the Republican primaries in 2015-16, and went on to work for Donald Trump’s presidential campaign. Another client of Cambridge Analytica was Leave.Eu, the successful campaign for British withdrawal from the European Union.